1. Field of the Invention
The present invention relates to a pipe rack forming method and apparatus.
2. Description of the Related Art
In the convention art, there has been a structure described in Japanese Unexamined Patent Publication (JP-A) No. 2001-9554 as a pipe rack forming apparatus for forming a rack tooth having a final tooth profile of a fixed tooth bottom height and tooth top height in a flat surface portion of a pipe forming body, in which the flat surface portion is previously formed in a part of a raw pipe material.
This prior art presses the flat surface portion of the pipe forming body by a tooth bottom forming surface having the same tooth profile portion as the final tooth profile in a tooth profile metal mold, in a state of holding the pipe forming body by a holding portion of a holding metal mold. It sequentially pressure inserts two or more mandrels having diameters from a small diameter to a large diameter to an inner periphery of the pipe forming body so as to press and move forward and backward in a repeated manner. Accordingly, a wall in the flat surface portion of the pipe forming body is casted up from a side of the inner periphery, whereby the rack tooth having the final tooth profile is formed on an outer periphery of the flat surface portion.
In the prior art, a plurality of mandrels of different sizes is required, and many man-hours of labor are required. Further, the flat surface portion of the pipe forming body is pressed by the tooth bottom forming surface having the same tooth profile portion as the final tooth profile in the tooth profile metal mold from the beginning. The mandrel is pressure inserted to the inner periphery of the pressed pipe forming body, so that the first mandrel is structured to have a particularly small diameter which is easily broken due to a buckling failure. Accordingly, the smaller the pipe rack is, the harder the formation becomes.
An object of the present invention is to easily form a pipe rack while avoiding breakage of the mandrel at a time of forming the pipe rack by using a tooth profile metal mold and the mandrel.
The present invention discloses a pipe rack forming method of forming a rack tooth having a final tooth profile of a fixed tooth bottom height and tooth top height, in a part of a raw pipe material. The pipe rack forming method prepares a tooth profile metal mold having plural stages of tooth profile portions with different height positions of tooth bottom forming surfaces. In a state of the steps include holding a raw pipe material by a holding portion of a holding metal mold, while pressing a part of the raw pipe material by the tooth bottom forming surfaces of the respective stages of tooth profile portions in the tooth profile metal mold. Sequentially tooth profile portions are employed in which the tooth bottom height applied to a part of the raw pipe material is reduced in sequence for the tooth profile portion in the tooth profile metal mold, repeatedly pressing and moving forward and backward a mandrel having the same size to an inner periphery of the raw pipe material every time when the respective stages of tooth profile portions in the tooth profile metal mold press a part of the raw pipe material, and forming a rack tooth having a final tooth profile.
The present invention discloses a pipe rack forming apparatus used for executing the pipe rack forming method with a tooth profile metal mold having plural stages of tooth profile portions. A holding metal mold has plural stages of holding portions individually corresponding to the respective stages of tooth profile portions in the tooth profile metal mold. A pipe pressing and holding means is present for pressing and holding a raw pipe material between the holding portion in the holding metal mold and the tooth profile portion in the tooth profile metal mold in each of the stages. A mandrel pressing and moving forward and backward means is present for pressing and moving forward and backward the mandrel to an inner periphery of the raw pipe material. The raw pipe material formed by using the front stage of the tooth profile portion in the tooth profile metal mold, is transferred between the holding portion in the rear stage of holding metal mold and the tooth profile portion in the tooth profile metal mold and is pressed and held by the pipe pressing and holding means. The mandrel is pressed and moved forward and backward to the raw pipe material by the mandrel pressing and moving forward and backward means.
The present invention also discloses a pipe rack forming apparatus used for executing the pipe rack forming method having a tooth profile metal mold with plural stages of tooth profile portions. A holding metal mold is present having one holding portion commonly corresponding to the respective stages of tooth profile portions in the tooth profile metal mold. A pipe pressing and holding means is present for pressing and holding a raw pipe material between the common holding portion in the holding metal mold and the tooth profile portion in each of the stages of tooth profile metal molds. A mandrel pressing and moving forward and backward means is also present for pressing and moving forward and backward the mandrel to an inner periphery of the raw pipe material. A rear stage of the forming portion in the forming metal mold is positioned with respect to the raw pipe material so as to be pressed and held by the pipe pressing and holding means while holding the raw pipe material formed by using the front stage of the tooth profile portion in the tooth profile metal mold in the holding portion in the holding metal mold. The mandrel is pressed and moved forward and backward with respect to the raw pipe material by the mandrel pressing and moving forward and backward means.
The present invention discloses a pipe rack forming method of forming, from a raw pipe material, a rack tooth having a final tooth profile of a fixed tooth bottom height and tooth top height, in a part of the raw pipe material. The method utilizes a tooth profile metal mold in which a tooth profile portion is capable of being displaced with respect to a tooth profile metal mold main body, and a height position of a tooth bottom forming surface in the tooth profile portion is capable of being controlled. The raw pipe material is held by a holding portion of a holding metal mold and a tooth profile metal mold main body of the tooth profile metal mold, while pressing a part of the raw pipe material by the tooth bottom forming surface of the tooth profile portion in the tooth profile metal mold. The tooth profile portion is controlled so that the tooth bottom height applied to a part of the raw pipe material by the tooth profile portion of the tooth profile metal mold is reduced in sequence, by repeatedly pressing and moving forward and backward a mandrel having the same size to an inner periphery of the raw pipe material every time when the tooth profile portion in the tooth profile metal mold presses a part of the raw pipe material, thereby forming a rack tooth having a final tooth profile.
The present invention also discloses a pipe rack forming method of forming, from a raw pipe material, a rack tooth having a final tooth profile of a fixed tooth bottom height and tooth top height, in a part of the raw pipe material. The method utilizes a tooth profile metal mold in which a tooth profile portion is capable of being displaced with respect to a tooth profile metal mold main body, and a height position of a tooth bottom forming surface in the tooth profile portion is capable of being controlled. The raw pipe material is held by a holding portion of a holding metal mold and a tooth profile metal mold main body of the tooth profile metal mold, while pressing a part of the raw pipe material by the tooth bottom forming surface of the tooth profile portion in the tooth profile metal mold. The tooth profile portion is controlled so that the tooth bottom height applied to a part of the raw pipe material by the tooth profile portion of the tooth profile metal mold is reduced in sequence, alternately repeating an operation of moving forward by pressing and moving backward by pressing a mandrel having the same size to an inner periphery of the raw pipe material every time when the tooth profile portion in the tooth profile metal mold presses a part of the raw pipe material, thereby forming a rack tooth having a final tooth profile.